This invention relates to electrical connective means within a cathode ray tube and more particularly to electrical contactor means for improving the electrical connection between the mask-member and the associated conductively coated panel of a color cathode ray tube.
Color cathode ray tubes as conventionally employed in television applications, usually have encompassing envelopes comprising integrations of neck, funnel, and face panel portions whereof the face panel includes an extensive viewing area upon which a patterned cathodoluminescent screen is disposed. The face panel is conventionally formed to have a substantially upstanding perimetrical sidewall therearound, the edge of which is hermetically joined to the seating edge of a compatibly shaped funnel portion by a sealing procedure during tube manufacturing. The interior of the panel, including the screen and the surrounding panel sidewall is usually metallized with a film of aluminum after formation of the patterned screen. This metallic film serves two functions: first, it provides a segment of the electrical conductive path for the screen potential, and secondly, the presence of the reflective film upon the back of the screen enhances the brightness of the color-emitting phosphors comprising the patterned imagery emanating therefrom. Spatially positioned within the face panel, is a multiple-opening mask member formed of a substantially domed apertured member, the edge of which is peripherally supported by an attached circumscribing framing member. This composite mask structure is supported within the face panel, in spaced relationship to the viewing area, by a plurality of suitable positional means attached about the frame member in a manner to mate with supporting studs embedded in and projecting from the wall of the panel.
Upon completion of the screen forming process, the mask-panel assembly is hermetically sealed to the funnel portion of the envelope. Electron generating means in the form of a structure embodying one or more electron guns, is then positioned and sealed within the neck portion of the envelope, whereupon the tube is subsequently evacuated and processed.
Under conventional operating conditions, the screen potential in a shadow-mask color cathode ray tube is substantially that of the final anode electrode of the electron gun structure, such being achieved by a diverse internal conductive path within the tube envelope. The final anode electrode of the gun structure usually makes electrical contact by supportive snubber means with an electrically conductive coating, such as Aquadag, which is applied to the interior surface of the funnel portion of the tube envelope. A relatively high voltage electrical potential is conventionally applied to this conductive coating by means of a button-type connection oriented in the wall of the aforesaid funnel portion. The other differential voltages required for the successful operation of the electron gun structure, are supplied to the respective electrodes therein by specific electrical conductive means terminating at the connective pins traversing the base portion. These pins, in turn, are connected to suitable voltage sources external of the tube. The final anode voltage, which is supplied to the conductive coating on the internal surface of the funnel, is connected to the apertured mask by a resilient contact member attached to the frame of the mask and extended therefrom to make pressured contact with the coating. Electrical connection between the mask and the screen of the tube is consummated through the spaced-apart mask positioners in conjunction with the mating supporting studs protruding from the panel sidewall and the aluminized film disposed thereon. The studs are usually kept free of aluminum to avoid the prevalence of metallic flakes resultant of subsequent mask positioning in the panel. Since the mask positioning means per se makes riding contact with the supporting studs, electrical connection between the mask and the aluminized panel is provided by applying an area of an additional conductive coating, such as Aquadag, to at least a portion of the stud proper to assure electrical contact between the stud and the adjacently disposed aluminum film on the panel sidewall. However, deleterious effects have been noted in the form of erosion between the Aquadag and the aluminum film, accidental splashing of Aquadag on the mask or screen, and the undesirable prevalence of loose particles and flakes of Aquadag in the vicinity of the mask and screen.